1. Field of the Invention
The present invention relates to a brake system of a vehicle such as an automobile, and more particularly, to a brake system for a behavior control of a vehicle, incorporating a pump for pressurizing a working fluid of the brake system, the pump being started before the start of the behavior control to provide a raised pressure source of the working fluid ready for the behavior control without any substantial accumulator therefor.
2. Description of the Prior Art
By Japanese Patent Application 7-201779 laid open to public as Laid-open Publication 8-150919 and having counterparts in U.S.A. and Germany as U.S. Pat. No. 5,797,663 and German Patent Application No. P19535623.3-21, respectively, there has been proposed a brake system for a behavior control of a vehicle such as an automobile adapted to operate with an automatic control means which controls a pump and a plurality of fluid flow control valves based upon a parameter representing a liability of the vehicle to an unstabilized running behavior, the pump generating a raised pressure source of a working fluid by operation, while the fluid flow control valves dealing with the raised pressure source to supply a raised pressure to selected one or ones of four wheels, so as, for example, to brake a front wheel at the outside of a turn running of the vehicle when it is liable to a spin, wherein the invention resides in that the brake system dispenses with the conventional accumulator for the pressurized working fluid by the pump being started to operate according to a forecast of the vehicle being put into the unstabilized behavior estimated by the automatic control means based upon the above-mentioned parameter approaching to a first predetermined value thereof indicating a probability of the occurrence of the unstabilized behavior so that a raised pressure source of the working fluid is immediately available with no substantial accumulator therefor when the automatic control means decides to supply the working fluid at a raised pressure to a wheel cylinder or cylinders of a particular wheel or wheels for execution of a stability control.
In the above-mentioned prior art, it is proposed to check if a parameter such as the slip angle of the vehicle body representing the liability of the vehicle to a spin has exceeded a first predetermined threshold value thereof to start the operation of the pump and to check if the parameter has exceeded a second predetermined threshold value thereof to start the execution of the stability control, the second threshold value being higher than the first threshold value.